> Then don't buy that device

Except when the device doesn't appear to be, but can be updated in a way that makes it obvious it does. Absolute statements like "all devices should be able to be jailbroken" or "I want things supported forever" or "just dont do x" are misguided. The world is more complicated, even on this issue. Any implemented solution will have holes and the world will be all the better for it. Progress requires things to die off.